Grain population emission in the IR: tTotal emission (black), a-C1 (blue), a-C2 (green), VSG (magenta),a-C:H/a-C (grey dot), and a-Sil/a-C (orange dot). Left panels: NaCo range between 3 and 4 μm. Middle and right panels: range covered by VISIR filters: 8.6, 10.4, and 11.3 μm. From top to bottom: decrease in G₀ values, which are 2 × 10⁶, 2 × 10⁵, and 2 × 10⁴. The corresponding distances to the star are 20, 75, and 200 au, respectively. The distance and G₀ ∕n_H are derived from Fig. 8.